In producing a fluoroester usable as a starting material for water- and oil-repellents, represented by the general formula (IV):Rf-CH2CH2OCOCX═CH2  (IV)wherein Rf is a perfluoroalkyl or polyfluoroalkyl group comprising 1 to 20 carbons and X is H or CH3, a process has been proposed which comprises reacting a fluoroalkyl iodide with a carboxylate represented by the general formula (III):CH2═CXCOOK  (III)wherein X is H or CH3 and K is an alkali metal (Japanese Examined Patent Publication No. 18112/1964). The process, however, generates as by-products a large amount of fluoroalkenes represented by the general formula (I):Rf-CH═CH2  (I)wherein Rf is a perfluoroalkyl or polyfluoroalkyl group comprising 1 to 20 carbons.
The fluoroalkenes can be used as a starting material for an organo-fluorosilane represented by the general formula (V):RfCH2CH2SiRnX3-n  (V)wherein Rf is a perfluoroalkyl or polyfluoroalkyl group comprising 1 to 20 carbons, R is an alkyl or aryl group and n is 0, 1, or 2 (Japanese Unexamined Patent Publication No. 126621/1975). However, the amount of the fluoroalkene required for producing the organo-fluorosilane is too small. Accordingly, the production efficiency can be improved if the excess fluoroalkene is converted into a fluoroalkyl iodide and recycled as a starting material for the above-mentioned fluoroester.
A process (dehydrohalogenation) is known which synthesizes Rf-CH═CH2 represented by the above-described general formula (I) from a fluoroalkyl iodide (Japanese Unexamined Patent Publication No. 69347/1992). However, in the reverse reaction of adding hydrogen iodide (HI) to Rf-CH═CH2, it is known that Rf-CHI—CH3 is generally obtained as a main product following Markovnikov rule while a process for efficiently synthesizing Rf-CH2CH2I not following Markovnikov rule is totally unknown.
Some reactions of adding hydrogen chloride (HCl) or hydrogen bromide (HBr) to a fluoroolefin have been reported such as a process using AlBr3 as a catalyst (J. Am. Chem. Soc., 72, 3369 (1950)), a process using CaSO4/C as a catalyst (J. Am. Chem. Soc., 75, 5618 (1953)), etc. However, the use of hydrogen chloride or hydrogen bromide poses problems: the reaction rate is extremely low; by-products such as polymers, etc. are formed. Therefore, such processes cannot be used in industrial syntheses.